A diagnosis of the presence of a lesion or the kind of a lesion by observing a tissue slice obtained from a human body with a microscope, so called a pathological diagnosis, has been actively performed. A tissue sample which is a target of pathological diagnosis is generally prepared so as to suit microscopic observation, through a fixation process, embedding process, slicing process, and staining process. In many techniques suggested in recent years, a high-magnification image data (a cell image) of a stained tissue slice has been generated using a microscope and image processing has been performed for the cell image in order to extract objects (such as cell nuclei) exactly.
For example, according to the technique described in Patent Document 1, the shapes of individual cells are intended to be extracted even when a plurality of cells overlap with each other on the cell image (see paragraph 0018). In this technique, specifically by focusing on the dyeing concentration (concentration gradient) of cells, the shapes of individual cells are intended to be extracted on the basis of positive or negative codes of an inner product value of a concentration gradient vector at a pixel constituting the outline of a cell and a displacement vector from the pixel to the center of the cell (see paragraphs 0027 to 0028, FIG. 10, paragraphs 0084 to 0088, FIGS. 13 to 16).
According to the technique described in Patent Document 2, effects of noises and edges of other tissues are intended to be removed in extracting the shapes of objects (cell nuclei) from a cell image (see paragraphs 0014 to 0015). Specifically, this technique is realized by a publically-known SNAKES processing performed to a blurred image and a non-blurred image (see paragraphs 0037-0039, FIG. 1, etc.), by a processing to paint a blank portion in a cell nucleus using the color around the blank portion in advance when there is a blank portion in the cell nucleus in the cell image (see paragraphs 0044 to 0046, FIG. 3, etc.), etc.